Blended pitch product and method of making



Feb. 11, 1936. s. P. MILLER BLENDED PITCH PRODUCT AND METHOD OF MAKING Filed July 24, 1933 EH ml INVENTOR JF/I/M/er BY I ATTORNEY Fatentecl Feb. 11, 1936 misc STATES PATENT GFFIQE AKING- Stuart Parmelec Miller, Englewood, N. J assignor to The Barrett Company, corporation of New Jersey New York, N. Y., 2.

Application July 24, 1933, Serial No. 682,034

In Canada July 19, 1928 12 Claims.

This invention relates to improved pitch products and is directed in particular to blended o1 cut-back pitch products, for instance, products obtained by blending hot coke oven tar pitch and 5 a flux, and to their production from tar.

This application is in part a continuation of my applications Serial No. 213,497, filed August 17, 1927, issued as U. S. Patent 1,925,150, Serial No. 326,769, filed December 18, 1928 issued as U. S. Patent 1,920,097; Serial No. 370,954, filed June 29, 1929; issued as U. S. Patent 1,921,300 and Serial No. 316,894, filed November 3, 1928 issued as U. S. Patent 1,921,300. Commercial pitch products and more especially those pitch products to be used in road construction as binders or fillers, or as roofing pitches, etc., where they are subjected for an extended period of time to atmospheric conditions should contain as little of the low boiling tar constituents or tar constituents of intermediate boiling range as is compatible with technical requirements and commercial specifications in order to assure permanence of their original physical characteristics. If a pitch containing a relatively large proportion of such constituents is exposed tothe atmosphere for some time, evaporation results in contraction and hardening, or embrittlement, of the residue. Hence the presence of such constituents in large amounts has an undesirable efiect upon the aging qualities of the pitch. The presence of such constituents, however, is ordinarily necessary to give the pitch the desired melting point and plasticity.

The products of the present invention are cutback pitch products which do not require as great a proportion of the lowor intermediateboiling constituents to give them the required low melting point and plasticity as do corresponding hitherto-known cut-back pitch products, and which accordingly contain a greater proportion of high-boiling constituents for a given melting point than do the latter products. In accordance with my invention the products are prepared from a type of high-melting point pitch that, when cut-back with a given flux, gives products of lower melting point than do ordinary pitches of the same melting point when cut-back with the same amount of the same flux; hence pitches of this type may be employed in the product in correspondingly increased ratio.

Then again in the production of pitch for industrial purposes rigid specifications have frequently to be met; these may require, for example, that the free-carbon content, volatile oil content, viscosity, melting point, and other properties be within certain limits as will be hereinafter more fully described. In practice it is frequently diflicult or impossible to meet the required conditions by producing pitches by straight distillation of tar. By blending straightrun pitches of higher melting point than the desired product, however, with fluxes of various types and in various proportions, the desired commercial products can be made. The fluxes ordinarily used are coal tar products, e. g. raw tar, dehydrated tar, topped tar, semi-pitch, and pitches of various melting points.

The relative market values of the products used difier widely and vary with market conditions. In general oils are worth more When market conditions are such that the demand for tar-distillate oils is high, it is advantageous to use a maximum of high-melting pitch and a minimum of flux in the production of a given product. duction of tar distillate in preparing the desired cut-back products, since the content of valuable distillate oils is much lower in high-melting pitch than in flux.

In carrying out this invention, the high melting pitch with which flux is to be blended (referred to in general as the base) is a coal-tar or water-gas-tar pitch having a high melting point, i. e. above about 250 F., and usually in the neighborhood of 300 mined by the method described by Weiss, J. Ind. and Eng. Chem., vol. 10, (1918) pages 820 to 822) It is a pitch of relatively low free-carbon content compared with ordinary pitches of the same melting point, and is made by a distillation method which minimizes decomposition. The flux may be of the types previously used in making outback pitch products, or may be another material compatible with the base.

Since prolonged heating, including such heating as is required to remelt a solidified pitch base, tends to decompose the base and increase its free-carbon content, molten flux is preferably blended with the base soon after the production of the base by distillation of tar and while the latter is still molten. The blending is advantageously carried out in a continuous manner.

Among the distillation methods by which bases may be prepared suitable for use in the present invention are distillation of tar by bringing it as a fine spray into direct contact with hot gases, for instance, hot fresh coal distillation gases at a temperature of 350650 as described more fully in my U. S. Patent 1,920,097 which, briefly, discloses the process of distilling tar to pitch having than pitch.

This permits a maximum pro- F. or above (as detergases passing through a tar still wherein the tar and pitch produced therefrom are sprayed and resprayed from a body of the tar in the bottom of the still into the gases passing therethrough in the form of a fine intense spray having sufiicient force to impinge against and wash the interior surfaces of the still, whereby distillation is effected with a minimum of decomposition; and distillation by heating a stream of tar, for instance to around 400 0., flashing it to remove part of the oil vapors, and subjecting the hot residue to high vacuum to further distill it by its residual latent heat as described more fully in U. S. Patent No. 1,759,816 to Alexander MacCubbin and Joseph Zavertnik.

It is preferred to blend the base directly as it is produced and while yet in a liquid condition with the desired flux, for instance a partly distilled coal tar, which also may be blended While yet hot after its production, 1. e. at a temperature above 50 C. and preferably at -300 C.

Pitch products of high free carbon content, i. e. 12% or more up to 25% for example, for road tars of around 100 F. melting point, or up to even 35% for roofing pitches of around 145 F. melting point, paving pitches, etc., may be prepared directly from coke oven tar according to this invention, without admixture with gas-house tar (i. e. tar produced when bituminous coal is coked in horizontal gas retorts) which is usually necessary at the present time in the preparationof pitches of high free carbon content.

Nevertheless other tars, for example gas-house tar and water gas tar, etc. may be used in preparing the pitch products. When such tars areused they are preferably used as components of the flux.

Pitch products prepared by blending a flux with a high melting point pitch of the type herein described will generally contain less fiux than products prepared from ordinary coal tar pitch of the same melting point, i. e. pitch prepared in an ordinary externally heated tank still or by heating in a pipe coil and flashing without the aid of reduced pressure. The new pitch products for a given melting point contain a larger proportion of high boiling pitch constituents than ordinary straight-run pitches of the same melting point, or than pitch products of the same melting point prepared by blending an ordinary pitch with flux.

lhe melting points of the commercial cut-back pitch products hitherto known to the art are dea melting point above 250 F. by means of hot terminable with a fair degree of accuracy by calculating the weighted average of the melting points of flux and base. For example,

Letting B'zparts by volume of base F=parts by volume of flux t=melting point of base in F t =melting point of fiux in F t2=me1ting point in "F of blended pitch product;

Then

Bt-i-Ft B-l-F 2 This formula does not apply to the products of the present invention. If the melting points of the new products actually determined are compared with melting points calculated by the above formula for such products, it is found that the actual melting point is considerably lower than. the calculated melting point. Stated in other terms, less flux is required to produce products of given melting point from bases of given melting point according to my invention than according to previously known methods. And,. although the bases employed have a lower free-carbon content than ordinary pitches of the same melting. point, the cut-back products in general have a higher free-carbon content for the same melting point than cut-back products prepared from the ordinary pitches. And as a corollary, former processes of producing pitches of as high free carbon content do not give the high oil yields obtainable by the method of this invention. It is characteristic of at least some of the pitch. products prepared from coke oven tar by the process of this invention that their free carbon. content, expressed in percent, is greater than one-eighth of their melting point expressed in degrees Fahrenheit, although not made from a high free carbon tar such as gas-house tar.

The following table illustrates this difference by specific examples of both the new and old products. In each example the figures indicating relative amounts of ingredients are calculated on a basis of 100 gallons tar as the initial amount of raw material. Thus parts (by volume) as given in the table are also percentages (by volume) based on total original tar and hence the data of the several examples are directly comparable.

Examples A B C D Y E F G H Base:

1. Parts tar 83.9 60.4 53.8 38.4 50.8

2. Parts distillation" 37.6 44. 7 39. 8 28.4 32.0

3. Parts (Straight distillation of 44.1 15.1 14.0 9.6 18.3

4. Melting point a mixture of 20-30% 176 400 389 400 296 Flux: gas house tar and 5. Parts tar 80-70% coke oven 16.1 39. 6 46. 2 61. 6 49. 2

6. Parts distillation tar). 0.4 4.0 2.2 4.9 4.4

7. Parts 16.5 35.2 44.0 56.1 44.3

8. Melting point 55 605 50 57 63. 5

9. Total distillation 30 17-18 12 38.0 48.7 42.0 33.3 36.4

10. Melting point by I weight, average formula. 144. 7 163 132 107 131 Pitch product:

11. l lelting point 145 94 144 105 94 105 12. Percent free carbon- 20.0 16.0 13.0 15. 3 19. 7 15.3 11.9 13. 1

13. Yield 70 83-82 88 59.6 50.3 58.0 65.7 62.6

Numerals 1 to 4 in the table relate to the base of pitch, and numerals 5 to 8 relate to the flux which is blended with the base to form the pitch product described opposite numerals 11 to 14. Numerals 1 and 5 indicate the parts of tar which are distilled to produce the base and flux respectively, and numerals 2 and 6 indicate the parts of distillate obtained. The total distillate opposite numeral 9 equals the sum of the distillate opposite numerals 2 and 6 for each example. Numerals 3 and 7 give the parts of base and fiux which result from the distillation and which are blended to produce the pitch products. Parts are given in parts by volume throughout the table. Numeral 4 gives the melting point of the base in degrees Fahrenheit and numeral 8 gives the melting point of the flux in degrees Fahrenheit. The melting point of the pitch product is given opposite numeral 11. The melting point as determined by the formula for weighted averages given above is shown opposite numeral 10. The percent by weight of free carbon is given opposite numeral 12.

Numeral 14 shows the percent of primary 400 F. pitch ingredients (P. I.) present in the final product figured on the basis that the tar from which the pitch product is obtained represents 25% of such primary 400 F. pitch ingredients. Primary 400 F. pitch ingredients may be defined as that portion of tar which remains as a residue when tar is distilled to pitch of 400 F. melting point by a method which minimizes decomposition, e. g. by spray or vacuum distillation as above described. Average coke oven tar contains approximately 20-25% by volume of such constituents. Using the value 25% for the tars treated in the examples the volume percentage content of primary 400 F. pitch ingredients is readily calculated from the volume yield of the pitch product, which is given opposite numeral 13 and which for each of the Examples D to H inclusive equals the sum of the values opposite numerals 3 and '7. For example, in column D the pitch yield is 59.6 and the amount of primary pitch ingredients equals 25% of items 1 and 5 which is 25. 25+59.6=41.9, the percentage content of 400 F. pitch ingredients.

The first three examples, A, B, and C, indicate the character and yield of products obtained by the straight distillation of a mixture of gas house tar and coke oven tar to produce roofing pitch and road tars of the penetration, binder and heavy surface treatment types, respectively. The figures given in these three examples are not taken from any specific runs but represent a general average of many runs.

Example B indicates an average yield obtained by distillation in a pipe still. When pitch of this melting point is produced by straight-run distillation by spraying tar into a current of hot gases, a distillate yield of 22 or 23% may be obtained.

Example D represents a roofing pitch of the prior art prepared entirely from coke oven tar by distilling the tar in a pipe still to produce flux and base, and blending the flux and base thus produced. The low carbon content is typical, for a pitch of this melting point. The melting point when figured by the law of weighted averages corresponds closely with the actual melting point.

Example E represents one of the new pitch products of this invention. It is a pitch suitable for roofing purposes. Pitch of high melting point obtained by the distillation of coke oven tar in the manner described in my copending application Serial No. 326,769 (U. S. Patent 1,920,097) is blended while still hot and fluid with a stripped coke oven tar. A much higher distillate oil yield is obtained than in Example D, although the pitch product is of substantially the same melting point. The content of primary 400 F. pitch ingredients in the pitch product is much higher than in the product of Example D. The melting point of the new pitch product as determined by the formula of weighted averages does not all agree with the melting point obtained in practice, as is evident from the table.

The comparative yields of total distillate as shown opposite numeral 9 of the table illustrate the relatively large yields of distillate obtained by the process of this invention.

Examples F, G, and H are examples of road tars, namely a heavy surface treating material, G, and penetration binders F and H, prepared by the process of this invention. On comparing Examples F, G, and H with Examples B and C with respect to the oil yields obtained, the superiority of the process from the standpoint of high oil yield is readily seen. The oil yield is high and the yield of pitch per 100 parts of tar is correspondingly low. The products of Examples F, G, and H were obtained from coke oven tar without admixture with gas-house tar or other tar of high carbon content.

The melting points opposite numeral l0 were computed by substituting the values for the base and flux in the formula given above. For example, the value for Example D was obtained from the equation 44.1 (176)+(l5.5) (55) MP 44.1+15.5

The melting points for the other products given opposite numeral were calculated in a similar manner.

While it has been impossible so far to determine the precise reasons for the difference in properties between the old and new products, it may possibly be accounted for as follows: A pitch base, for example of 350 F. melting point, as used in the present invention, consists of a complex mixture of constituents comprising true free carbon, so-called free-carbon (as determined according to Weiss, J. Ind. and Eng. Chem. vol. 10, (1918), pages 820-822, or well known modifications of this method), and heavy hydrocarbons; these categories overlap to some extent. A pitch base of the same melting point, 350 F., but produced according to the methods hitherto customary in manufacturing cut-back products, contains all these ingredients and in addition a considerable amount of thermal decomposition products, in part indicated usually by increased free-carbon content. These products are probably less soluble or less easily dispersed in a given flux than the primary pitch constituents. Consequently, when a given amount of the old type of base is blended with a given amount of flux, a less homogeneous product is obtained than under comparable conditions with the new type of flux. This condition may obtain even with comparable free-carbon contents in the products, since the decomposition products referred to do not all necessarily appear as free-carbon.

Since increased non-homogeneity of such mixes is usually accompanied by increased viscosity, the old, less homogeneous products have a higher melting point, the melting point of pitch, when determined as described, being in eifect a viscosity-temperature determination.

This probable explanation is offered to clarify the observed differences between the old and new products and is not intended to limit the invention in any way.

Both the old and new cut-back products are exceedingly complex chemical mixtures and it is impossible with available knowledge to define and difierentiate them on a precise basis of chemical composition. An empirical definition may, however, be based on their content of primary 400 F. melting point pitch constituents.

The relative quantities of such constituents in typical pitch products of the present invention and in ordinary straight-run and cut-back pitches are illustrated opposite numeral 14 of the table.

In the drawing the melting points of pitches known to the prior art and the new pitch products have been plotted against their content of primary 400 F. pitch ingredients and a line is shown which divides the new products of this invention from the old. In the products of Examples A, B, and C, each of which represents the average or many pitches prepared by straight distillation, the percentage content of primary 400 F. pitch ingredients is less than in the new pitch products of the same melting point and the yield of distillate obtained in their preparation is less than the yield of distillate obtained when pitches of the same melting point are prepared by the new process.

Example D is representative of the pitches prepared by the old so-called cut-back methods in which a base is blended with a flux. The base in this case was pitch with a melting point of 176 F. prepared by distilling tar in a pipe still. The flux was also prepared by distilling tar in a pipe still.

The pitch products of Examples E, F, G, and H were each prepared by blending liquid pitch of high melting point directly after its formation by spraying coke oven tar into hot fresh coke oven gases with hot liquid flux which was formed by contacting the tar with hot gases in a baiile tower and conducting the hot liquid residue directly into the blending chamber before it became solid. Pitches prepared in this manner have a higher content of primary 400 F. pitch ingredients than the pitches of the prior art and in the preparation of these pitches a higher yield of distillate is obtained than in the production of pitches of the same melting point by the old methods.

The products are all relatively high in primary 400 F. pitch ingredients. In general, the higher the melting point, the higher the content of primary 400 F. pitch. In the drawing the examples shown in the table have been plotted using the content of primary 400 F. pitch ingredients as abscissae and the melting point in degrees Fahrenheit as the ordinates. The new compounds have a content of primary 400 F. pitch ingredients greater than that represented by a: in the equation, y=4.r30 and generally less than represented by a: in the equation 3;: 4:c 100.

Although the preparation of roofing pitch and road tars and the properties of these blended products have been more particularly described, the invention is not limited thereto, but includes other pitches such as briquette pitch with a melting point of, for example, 185 F. In general the present invention comprehends pitch products having melting points between F. and 200 F.

The uses for which the products are applicable will differ with differing melting points. Those products having melting points of 80 to 110 F. are especially suitable for use as soft road binders. The float test of such products as determined by the A. S. T. method ordinarily lies between and 150 seconds at 32 C. Products having melting points of 100 to 120 F., especially to F., are suitable for use as penetration binders, soft joint fillers, etc. The float test on these products may vary from around 160 to 200 seconds at 50 C. Products of melting point around to F. are particularly adapted for use as rooiing pitches, etc. Higher melting pitches may be used for making briquettes and for similar purposes.

Throughout the specification and claims pitch melting points are expressed in degrees Fahrenheit as determined by Tests D6 and D7 published in The Journal of Industrial and Engineering Chemistry, vol. X, pages 820 to 822 (October, 1918). Free carbon contents are expressed as percentage, as determined by the method of the American Society for Testing Materials, Serial Designation D4-2'7.

By the expression tar flux as used in the appended claims is meant a flux comprising essentially tar (including raw and topped tar), tarry oil, or partly distilled tar (sometimes designated as semi-pitch). Pitch also may be used as the iiu-x, especially for the preparation of high melting point products. The pitch flux should have a melting point substantially below the melting point of the desired product and for the preparation of to 200 F. melting point products may have as high as 140 F. melting point although, in general, lower melting fluxes are to be preferred. Cut-back products for normal use for the described purposes will contain not more than about 40% of pitch where the pitch used has a melting point in the neighborhood of 400 F.; lower melting pitches, of course, may be used in correspondingly higher proportions.

I claim:

1. A pitch product having a melting point above about 80 F. and less than (4x-36) F., where :1: equals the volume percentage of primary 400 F. melting point pitch ingredients present in the product.

2. A pitch product having a melting point, '1, between about 80 F. and about 200 F. and a volume percentage of primary 400 F. melting point pitch ingredients greater than 3. A pitch product having a melting point, y, between about 80 F. and about 200 F. and a volume percentage of primary 400 F. melting point pitch ingredients greater than said product being obtainable by distilling a member of the group consisting of coal tar and water gas tar to high melting point pitch by a method that minimizes decomposition and blending the pitch with a tar flux, the ratio of pitch to flux beging greater than that required to produce a product of the same melting point from ordinary pitch of melting point the same as said first-mentioned pitch.

4. A coal tar pitch product having a melting point, y, between about 80 F. and about 200 F. and a volume percentage of primary 400 F. melting point pitch ingredients greater than said product being obtainable by distilling tar to pitch having a melting point about 250 F. by a method that minimizes decomposition and blending the pitch with a tar flux, the ratio of pitch to flux being greater than that required to produce a product of te same melting point from ordinary pitch of melting point the same as said.

first-mentioned pitch.

5. A coke oven tar product having a melting point, 3;, above about F. and a volume percentage of primary 400 F. melting point pitch ingredients greater than said product being obtainable by distilling coke oven tar to pitch having a melting point above 250 F. by spraying the tar into hot gases, blending the pitch while yet hot and fluid with a flux comprising partly distilled coke oven tar, the ratio of pitch to flux being greater than that required to produce a product of the same melting point from ordinary pitch of melting point the same as said first-mentioned pitch.

6. A road binder having a melting point, y, between about 80 F. and about F. and a volume percentage of primary 400 F. melting point pitch ingredients greater than said binder being obtainable by distilling coke oven tar to pitch having a melting point above 300 F. by a method that minimizes decomposition and blending the pitch while yet hot and fluid with coke oven tar flux the ratio of pitch to tar flux being greater than that required to produce a product of the same melting point from ordinary pitch of melting point the same as the said first-mentioned pitch.

'7. A roofing pitch having a melting point, 11/, between about F. and about F. and a volume percentage of primary 400 F. melting point pitch ingredients greater than said roofing pitch being obtainable by distilling a member of the group consisting of coal tar and water gas tar to pitch having a melting point above 300 F. by a method that minimizes decomposition and blending the pitch while yet hot and fluid with a flux comprising partly distilled tar the ratio of pitch to flux being greater than that required to produce a product of the same melting point from ordinary pitch of melting point the same as said first-mentioned pitch.

8. A coke oven tar pitch product having a melting point between about 80 F. and about 200 F. and a percentage free carbon content numerically greater than the melting point in F degreeS, said product being obtainable by distilling coke oven tar to pitch having a melting point above 300 F. by spraying the tar into hot gases and minimizing decomposition, and blending the pitch while yet hot and fluid with a coke oven tar flux the ratio of pitch to flux being above that required to produce the product of the same melting point from ordinary pitch of melting point the same as said first-mentioned pitch.

9. A method of producing a blended pitch prodnot which comprises distilling coal tar to pitch having a melting point above 250 F. by spraying the coal tar into hot gases in such a manner as to minimize decomposition during the distillation and blending the pitch while yet hot and fluid with a fiux of the group consisting of coal tar, coal tar pitches, and coal tar oils.

10. A method of producing a blended pitch product from coke oven tar, which comprises distilling coke oven tar to pitch having a melting point above 250 F. by spraying the coke oven tar into hot gases and minimizing decomposition of the coke oven tar and the molten pitch, and. blending the pitch while yet hot .and fluid with a coke oven tar flux, the ratio of pitch to flux being greater than that required to produce a product of the same melting point from ordinary pitch of melting point the same as said first mentioned pitch.

11. A coke oven tar product having a melting point, y, between about 80 F. and about 200 F. and a volume percentage of primary 400 F. melting point pitch ingredients between x +36) /4 and (11+ 100) /4, sad product being obtainable by distilling coke oven tar to pitch having a melting point above 250 F. by spraying the tar into hot gases, blending the pitch while'yet hot and fluid with a flux comprising partly distilled coke oven tar, the ratio of pitch to flux being greater than thatrequired to produce a product of the same melting point from ordinary pitch of melting point the same as said first-mentioned pitch.

12. The method of producing a blended pitch product from coal tar which comprises distilling coal tar to pitch having a melting point above 250 F. by means of hot gases passing through a tar still wherein the tar and pitch produced therefrom are sprayed and resprayed from a body of the tar in the bottom of the still into the gases passing therethroughin the form of a fine intense spray having sufficient force to impinge against and wash the interior surfaces of the still whereby distillation is effected with a minimum of decomposition and blending the pitch while yet hot and fluid with a flux of the group consistingof coal tar, coal tar pitches, and coal tar oils.

STUART PARMELEE MILLER.

CERTIFICATE OF CORRECTION. Patent No. 2,050,528. February 11, 1936.

STUART PARMELEE MILLER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1 first col umn, line 11 for the patent number "1,921 ,500" read l,9/9,046; page 5, first column, line 2, claim 4, for "about" read above; and second column, line 35, claim ll for "sad read said; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 7th day of April A. D. 1956.

Leslie Frazer Acting Commissioner of Patents; 

